Soft X-ray Induced Photoreduction of Organic Cu(II) Compounds Probed by X-ray Absorption Near-Edge (XANES) Spectroscopy

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• 作者：Jianjun Yang ; Tom Regier ; James J. Dynes ; Jian Wang ; Jiyan Shi ; Derek Peak ; Yidong Zhao ; Tiandou Hu ; Yingxu Chen ; John S Tse
• 刊名：Analytical Chemistry
• 出版年：2011
• 出版时间：October 15, 2011
• 年：2011
• 卷：83
• 期：20
• 页码：7856-7862
• 全文大小：898K
• 年卷期：v.83,no.20(October 15, 2011)
• ISSN：1520-6882

文摘

Photoreduction is a major obstacle for using the X-ray absorption near-edge structure (XANES) fingerprint to perform metal speciation at the molecular level in biological and environmental samples, especially for metalloproteins. In this study, soft X-ray induced photoreduction was observed in organic Cu(II) compounds during XANES measurements in a third-generation synchrotron source. Next Cu L₃-edge, O K-edge, and C K-edge XANES spectroscopy, together with the scanning transmission X-ray microscopy (STXM), were used to probe the specific radiation damage processes of Cu acetate with similar local structures to Cu metalloproteins. Breakup of the Cu鈥揅u bond was hypothesized for the initial photoreduction of Cu acetate. The following radiation damage of Cu acetate produced CuO and an organic Cu(I) compound with a C鈺怌 bond, and the further photoreduction of the resulting CuO to Cu metal was also demonstrated. Our results indicated the importance of consideration of photoreduction during soft XANES measurements for the solid state compounds with high valence metals. Reducing the radiation dose to 0.1 MGy effectively prevented the photoreduction of organic Cu(II) compounds during these measurements. This proposed radiation damage mechanism in Cu acetate may be generally useful in explaining the photoreduction process in Cu metalloproteins.